Self-sealing tires with sealants applied to the inner surfaces thereof have been known as puncture resistant pneumatic tires (hereinafter, pneumatic tires are also referred to simply as tires). Sealants automatically seal puncture holes formed in such self-sealing tires. Various studies on sealants have been made.
Non-halogenated butyl rubber free of halogens is widely used as a rubber component in sealants. However, since non-halogenated butyl rubber having no crosslinking points is difficult to crosslink, it is crosslinked with zinc oxide as a metal crosslinker in the conventional production of tires. Such a crosslinking reaction needs to be carried out under relatively long time conditions such as 12 minutes at 170° C.